How is stress defined in mechanical engineering?

In mechanical engineering, stress is defined specifically as the force applied per unit area on an object. This definition encapsulates the fundamental concept of how external forces affect materials. When a force is applied to a material, it creates an internal resistance that is spread out over the area on which the force acts. This relationship is crucial in understanding how materials deform and ultimately fail when subjected to different loads.

Understanding this helps engineers to design safe and efficient components by calculating and predicting material behavior under various loading conditions. By measuring stress, engineers can also make informed decisions about material selection, ensuring that the chosen materials can withstand the forces they will encounter during service without failing. This definition is the foundation of applying concepts such as yield strength, tensile strength, and other material properties in engineering design and analysis.